In a printhead module comprising a plurality of nozzles, there is always the possibility that a manufacturing defect, or over time in service, will cause one or more nozzle to fail. A failed nozzle can sometimes be corrected by error diffusion or color replacement. However, these solutions at best provide approximations of the color missing due to the defective nozzle.
The chances of a nozzle defect increases at least linearly with the number of nozzles on the printhead module, both through the increase in sample space for a failure to occur, and the reduction in nozzle size which requires higher tolerances. Defective chips reduce yield, which increases the effective cost of the remaining chips. Nozzles that fail in chips in service increase the costs of providing warranty cover.
It may also be desirable to reduce the rate at which nozzles fire in printhead. This may be, for example, to reduce thermal problems or can be the result of the desired nozzle fire rate exceeding the rate at which any given nozzle can fire.
The Applicant has designed a printhead that incorporates one or more redundant rows of nozzles. It would be desirable to provide a printer controller capable of providing data to such a printhead.